The present invention relates to an anti-reflective layer and method for manufacturing a semiconductor device using the same, and more particularly, to an anti-reflective layer formed by a using resist composition and a method for manufacturing a semiconductor device using the same.
It is well known that fine patterns of a semiconductor device are formed by using photolithography. A schematic method for manufacturing patterns using the photolithography is as follows.
First, on a substrate desired to be patterned such as a semiconductor wafer, a dielectric layer or a conductive layer, a photoresist film made of organic materials which has the characteristic of changing its solubility to an alkaline solution before and after exposure to ultraviolet (UV) light, X-ray radiation etc. is formed. The resist film is selectively exposed by employing a mask pattern above the photoresist film, and then is developed to remove the portion having high solubility (in the case of a positive resist, removing the exposed portion) and leave the portion having low solubility to form resist patterns. Etching the substrate of the portion on which the resist has been removed to form patterns, and then removing the remaining resist, gives desired patterns for wiring, electrodes, etc.
Since fine patterns of high resolution can be obtained, the patterning method by the above-described photolithography is widely used. However, in order to form finer patterns, still further improvements in the manufacturing process are necessary.
The linewidth of the fine patterns formed after exposing and developing the photoresist film is required to be the same with that of the photomask at a particular reduction ratio. However, since many steps are needed in photolithography, it is very difficult to keep the linewidth of the patterns consistent. The variation of the linewidth is mainly due to a) the difference of exposing dosage owing to the difference of the thickness of resist, and b) light interference due to the diffused reflection of the light over the topography (S. Wolf and R. N. Tauber, Silicon Processing for the VLSI Era, Vol.1, p439, 1986).
Recently, the miniaturization of systems utilizing complex integrated circuitry has required chip-designed circuits of a far smaller size. Such a decrease in size, or an increase in capacity necessitates a miniaturization in the photolithography process, which could be satisfied with the use of more even topography and light of shorter wavelength.
However, the use of the higher frequency light as the exposure source results in a new problem. For example, a KrF excimer laser and DUV (deep UV) light which are expected to be used for manufacturing 256M bit DRAM (dynamic random access memory) have a shorter wavelength than the g-line, i-line, etc. If such light is used as the light source, certain defects, namely, those attributable to the reflections from a sub-layer having an uneven surface, become influential. That is, the CD difference occurs due to interference or a diffused reflection from the surface having an uneven topography.
To solve the above-mentioned problems, the coating of an anti-reflective layer is considered inevitable.
An anti-reflective layer is disclosed in U.S. Pat. No. 4,910,122. The layer is employed under a photosensitive layer such as photoresist and serves to exclude the defects attributed to the reflected light. The layer contains light absorbing dye components and is formed as an even and thin layer, so sharp photosensitive layer patterns can be manufactured by employing such a layer since the layer may absorb the light reflected from the substrate, as in a conventional method.
However, the conventional anti-reflective layer for DUV light has complicated components and limits in choosing materials. This raises production cost and makes its application difficult.
As one example of the conventional anti-reflective coating composition, a six-component mixture composition of polygamic acid, curcumin, bixin, sudan orange G, cyclohexanone and N-methyl-2-pyrrolidone is disclosed in the above-mentioned U.S. patent. This composition consists of four compounds of dye which absorb light of a specific wavelength and two solvents to dissolve the four compounds. From the exemplified composition, it is known that the composition is quite complicated and its preparation is not an easy task. Moreover, since the composition consists of many components, the problem of intermixing with the resist composition coated on the surface of the anti-reflective layer occurs, resulting in an undesirable product.